1. Field of the Invention
The present invention relates to an apparatus and method for collecting and channeling ground water, and more particularly, to a unit for water management that combines an extraction unit to absorb liquid from the ground, a method to transfer the liquid into a conduit, and a conduit system to carry the water away, without the need for separate components. The apparatus may be used for drainage or as an irrigation system.
2. Description of Related Art
Conventionally, most drainage systems used for water management for example on farms, sports fields, golf courses, civil engineering projects such as tunnels, road beds and retaining walls are primarily comprised of permeable drain pipes which have a number of small openings or pores distributed over the upper portion of the pipe so that water may enter through the upper portion and collect in the lower portion of the pipe. However, such systems are prone to becoming clogged with soil particles and the collection capability quickly becomes reduced. Various additions such as filters have been tried to prevent soil from entering the pipe. However, clogging still tends to occur.
To overcome this, a drain belt was developed as disclosed in U.S. Pat. No. 5,934,828 and sold as Capiphon drain belt. The drain belt is an efficient method for ground water collection without transferring soil particles into the drainage system. Thus, the drain belt does not become clogged and the collection capacity is not reduced over time. Further, the system does not require maintenance to de-clog pipes.
Such a drain belt 10 is shown schematically in FIG. 1. The surface of the belt 10 has a plurality of parallel slots 12 of generally rectangular cross-section which extend along the length of the belt 10. Each slot 12 communicates with a corresponding notch or channel 11 of generally circular cross-section forming, in combination, key-hole shaped cross-section extending along the length of the belt 10 and into the interior of the belt. The slots 12 and channels 11 are sized such that water is drawn into channels 11 via the slots 12 by capillary action so that it can be channelled along the length of the belt 10 and subsequently delivered into a pipe system to be drained away. When the belt 10 is installed in soil and the soil becomes saturated, water fills the spaces between the soil particles and also fills the channels of the drain belt 10 by capillary action.
FIG. 2a shows an end view of drain belt 10 in dry soil. Air fills the slots 12 and channels 11. FIG. 2b shows the drain belt 10 in saturated soil. Water fills the space between the soil particles and the slots 12 and channels 11. The water may flow along the channels 11 in the belt 10 to be discharged. The drain belt 10 construction means that water will be collected from any saturated soil in which it is installed.
FIG. 3 illustrates the collection area of a width of drain belt 10. As the water in the immediate vicinity of the drain belt moves into the channels 11 through the slots 12, and is removed, it is replaced with additional water moving in to fill the area vacated by the collected water. The speed of water movement towards the collection area is limited by the size of the pore spaces between the soil particles (hydraulic conductivity of the soil) and the pressure (head).
The efficiency of a drainage system is improved when the collection and discharge rate is greater than the ability of the soil to provide water for collection. The collection rate of drain belt can be increased or decreased by increasing or decreasing the length of the drain belt, since increasing the length provides a larger surface area for collection. Increasing the collection capacity is effective only if the additional water collected can flow through the channels 11 easily and can be discharged at the same rate as collection. The small size of the channels 11 create resistance to flow along the length of the belt, and since the drain belt must discharge through one end the drainage capacity is reduced to a small amount even though the collection capacity has been increased.
A functional drainage system requires efficient collection of the water, but also efficient transport of the water to the evacuation point. The small size of the channels 11 are not a practical transport mechanism for the collected water, and as such, the drain belt must be connected to a pipe network. The combination of the drain belt for water collection and the pipe network to transport the water, forms an effective drainage system, but is complicated, expensive, and prone to workmanship error.
Efficiency of the drainage system can be improved by increasing the frequency of drain belts, and thus, the frequency of discharge points, and by limiting the length of the drain belt so that the transport distance is short and the water is discharged into the pipe sooner. FIG. 4 shows a drainage system which can collect and discharge water rapidly, but is complicated and labor intensive to assemble and install. Both the pipe 20 and drain belts 10 must be sloped to drain by gravity, requiring extensive and careful excavation and backfilling. The areas surrounding the pipe 20 and drain belts 10 must be carefully hand compacted to prevent a U-bend joint so that water from the drain belt no longer discharges from the belt into the pipe. FIG. 5a shows, in cross section, a belt 10 joined to a pipe 20, arranged so that water may flow from the belt 10 into the pipe 20. FIG. 5b shows, in cross section, a joint where the surrounding ground has settled resulting in a U-bend preventing water from being discharged into the pipe 20.
Further, installing the drain belt in damp, wet, and muddy conditions has increased difficulties. A small amount of weight applied to the top surface can easily push the bottom surface into the soft earth and completely clog the slots 12 and channels 11, rendering the drain belt inoperative. Also, since the drain belt is installed in low areas where water collects, in trenches, the likelihood of foot traffic on the surface of the belt is unavoidable. Even installations over a layer of sand will display some obstructions in the slots 12 and channels 11.
As such, installation of a drain belt system is expensive because it requires careful supervision.